Electrochemical hydrogen pump

ABSTRACT

An electrochemical hydrogen pump includes at least one hydrogen pump unit including an electrolyte membrane, an anode on one main surface of the electrolyte membrane, a cathode on the other main surface of the electrolyte membrane, an anode separator on the anode, and a cathode separator on the cathode, the at least one hydrogen pump unit transferring, to the cathode, hydrogen supplied to the anode and pressurizing the hydrogen, a first fixing member for preventing movement of the cathode separator in a direction in which the cathode separator is stacked, a first end plate on the anode separator at one end in the stacking direction, a second end plate on the cathode separator at the other end in the stacking direction, and a first gas flow channel through which hydrogen in the cathode is supplied to a first space between the second end plate and the cathode separator.

BACKGROUND 1. Technical Field

The present disclosure relates to an electrochemical hydrogen pump.

2. Description of the Related Art

Considering environmental problems, such as global warming, and energyproblems, such as depletion of oil resources, hydrogen has been focusedon as a clean alternative energy source in place of fossil fuels.Essentially, burning hydrogen produces only water, carbon dioxide, whichcontributes to global warming, is not produced, and few quantities ofother compounds, such as nitrogen oxides, are produced. Thus, hydrogenis anticipated as a clean energy source. Fuel cells, an example ofdevices that use hydrogen highly efficiently as a fuel, have beendeveloped and widely used for automotive power sources and home powergeneration.

In an upcoming hydrogen society, development of technology for storinghydrogen at high density and transporting and using hydrogen in areduced volume at low cost is required in addition to development oftechnology for producing hydrogen. In particular, to encourage thespread of such fuel cells as distributed energy sources, a hydrogensupply infrastructure needs to be established. Furthermore, varioussuggestions, such as methods for producing and purifying hydrogen andstoring purified hydrogen at high density, have been made to provide astable hydrogen supply.

For example, Japanese Unexamined Patent Application Publication No.2006-70322 suggests a high-pressure hydrogen producing apparatus. Thehigh-pressure hydrogen producing apparatus includes a stack of a solidpolymer electrolyte membrane, power feeders, and separators, with thestack sandwiched between end plates and fastened by fastening boltspassing through the endplates. In the high-pressure hydrogen producingapparatus, when a difference between the pressure applied to the cathodepower feeder on the high-pressure side and the pressure applied to theanode power feeder on the low-pressure side increases to a predeterminedvalue or higher, the solid polymer electrolyte membrane and the anodepower feeder on the low-pressure side deform. As a result, the contactresistance between the cathode power feeder on the high-pressure sideand the solid polymer electrolyte membrane increases.

Thus, the high-pressure hydrogen producing apparatus of JapaneseUnexamined Patent Application Publication No. 2006-70322 includes apressing unit, such as a disc spring or a coil spring, that presses thecathode power feeder on the high-pressure side to make the cathode powerfeeder adhere to the solid polymer electrolyte membrane if the solidpolymer electrolyte membrane and the anode power feeder on thelow-pressure side deform. Accordingly, an increase in the contactresistance between the cathode power feeder on the high-pressure sideand the solid polymer electrolyte membrane is suppressed.

SUMMARY

In the prior example, however, an increase in the contact resistancebetween the cathode separator and the cathode in a case where the gaspressure in the cathode increases is not fully investigated. One aspectof the present disclosure is developed in consideration of theforegoing, and one non-limiting and exemplary embodiment provides anelectrochemical hydrogen pump that can easily and appropriately suppressan increase in the contact resistance between the cathode separator andthe cathode of a hydrogen pump unit, compared with that in the priorart.

To solve the foregoing, in one general aspect, the techniques disclosedhere feature an electrochemical hydrogen pump that includes at least onehydrogen pump unit including an electrolyte membrane, an anode incontact with one main surface of the electrolyte membrane, a cathode incontact with the other main surface of the electrolyte membrane, ananode separator stacked on the anode, and a cathode separator stacked onthe cathode, the at least one hydrogen pump unit transferring, to thecathode, hydrogen contained in a hydrogen-containing gas supplied to theanode and pressurizing the hydrogen, a first fixing member forpreventing movement of the cathode separator in a direction in which thecathode separator is stacked, a first end plate disposed on the anodeseparator positioned at one end in the stacking direction, a second endplate disposed on the cathode separator positioned at the other end inthe stacking direction, and a first gas flow channel through whichhydrogen in the cathode is supplied to a first space formed between thesecond end plate and the cathode separator.

An electrochemical hydrogen pump according to one aspect of the presentdisclosure exhibits the advantage of easily and appropriatelysuppressing an increase in the contact resistance between the cathodeseparator and the cathode of the hydrogen pump unit, compared with thatin the prior art.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an image of an exemplary electrochemical hydrogen pump;

FIG. 1B is an image of an exemplary electrochemical hydrogen pump;

FIG. 2A is an image of an exemplary electrochemical hydrogen pumpaccording to a first embodiment;

FIG. 2B is an enlarged view of portion IIB of FIG. 2A;

FIG. 3A is an image of an exemplary electrochemical hydrogen pumpaccording to the first embodiment;

FIG. 3B is an enlarged view of portion IIIB of FIG. 3A;

FIG. 4 is an image of an exemplary electrochemical hydrogen pump in amodified example of the first embodiment;

FIG. 5 is an image of an exemplary electrochemical hydrogen pumpaccording to a second embodiment; and

FIG. 6 is an image of an exemplary electrochemical hydrogen pump in amodified example of the second embodiment.

DETAILED DESCRIPTION

In the high-pressure hydrogen producing apparatus of Japanese UnexaminedPatent Application Publication No. 2006-70322, the stack is fastened byfastening bolts passing through end plates and compressed in a stackingdirection. However, the inventors conducted thorough investigation andfound that high gas pressure in the cathode deforms the cathodeseparator so as to curve toward the neighboring end plate andaccordingly that the end plate also deforms so as to curve outward awayfrom the stack. In a plurality of such stacks, the cathode separatorpositioned at the end of the plurality of stacks in a stacking directiondeforms so as to curve toward the neighboring end plate. Accordingly,the end plate deforms in the same manner as described above.

The above deformation of the cathode separator forms a gap between thecathode separator and the cathode power feeder that is larger than thegap described in paragraph [0020] of Japanese Unexamined PatentApplication Publication No. 2006-70322. To fill the gap, the distance ofthe disc spring electrically connecting the cathode power feeder and thecathode separator to each other increases, and thus, the electricalresistance of the disc spring increases.

The foregoing can be seen not only in the high-pressure hydrogenproducing apparatus of Japanese Unexamined Patent ApplicationPublication No. 2006-70322, but also in an electrochemical hydrogen pumpin a prior patent of the applicant.

For example, as shown in FIG. 1A, a structure is suggested in which acathode gas diffusion layer 114 is accommodated in the concave portionof a cathode separator 116 and in which a portion of the cathode gasdiffusion layer 114 protrudes by a predetermined amount Ecd from theconcave portion in a thickness direction before a stack 500 of anelectrolyte membrane 111, a cathode catalyst layer 112, an anodecatalyst layer 113, the cathode gas diffusion layer 114, and an anodegas diffusion layer 115 is fastened.

When the stack 500 is fastened, the cathode gas diffusion layer 114elastically deforms by the amount of protrusion Ecd in a thicknessdirection, as shown in FIG. 1B.

During the operation of the electrochemical hydrogen pump, when the gaspressure in the cathode gas diffusion layer 114 of the stack 500increases, high pressure is applied to the anode gas diffusion layer115, the anode catalyst layer 113, and the electrolyte membrane 111,since the electrolyte membrane 111 prevents gas permeation. Then, theanode gas diffusion layer 115, the anode catalyst layer 113, and theelectrolyte membrane 111 are each compressed and deform. However, thecathode gas diffusion layer 114 elastically deforms in a direction inwhich the thickness T2, which is the thickness after compression by afastener, returns to thickness T1, which is the thickness before thecompression, so that the contact between the cathode catalyst layer 112and the cathode gas diffusion layer 114 can be appropriately maintained.

When the gas pressure in the cathode increases, however, the cathodeseparator 116 deforms so as to curve outward toward the neighboring endplate (not shown), as described above, so that a gap is likely to beformed between the bottom surface of the concave portion of the cathodeseparator 116 and the cathode gas diffusion layer 114. To reliablyestablish electrical contact between the cathode separator 116 and thecathode gas diffusion layer 114, the amount of protrusion Ecd of thecathode gas diffusion layer 114 needs to be further increased,considering deformation of the cathode separator 116. As a result, whenthe gas pressure in the cathode increases, the dimension of the cathodegas diffusion layer 114 in a thickness direction increases andelectrical resistance of the cathode gas diffusion layer 114 in thethickness direction increases.

Such a problem occurs not only in the above prior patent of theapplicant, but also in a structure in which a cathode gas diffusionlayer is disposed on a flat surface of a cathode separator having noconcave portions.

The inventors found that forming a space between the cathode separatorand the second end plate disposed on the cathode separator thatcommunicates with the cathode easily suppresses the above-describedincrease in the electrical resistance between the cathode gas diffusionlayer and the cathode separator and have developed one aspect of thepresent disclosure as follows.

An electrochemical hydrogen pump according to a first aspect of thepresent disclosure includes at least one hydrogen pump unit including anelectrolyte membrane, an anode in contact with one main surface of theelectrolyte membrane, a cathode in contact with the other main surfaceof the electrolyte membrane, an anode separator stacked on the anode,and a cathode separator stacked on the cathode, the at least onehydrogen pump unit transferring, to the cathode, hydrogen contained in ahydrogen-containing gas supplied to the anode and pressurizing thehydrogen, a first fixing member for preventing movement of the cathodeseparator in a direction in which the cathode separator is stacked, ananode end plate disposed on the anode separator positioned at one end inthe stacking direction, a second end plate disposed on the cathodeseparator positioned at the other end in the stacking direction, and afirst gas flow channel through which hydrogen in the cathode is suppliedto a first space formed between the second end plate and the cathodeseparator.

According to such a structure, the electrochemical hydrogen pumpaccording to the present aspect can easily and appropriately suppress anincrease in the contact resistance between the cathode separator and thecathode of the hydrogen pump unit, compared with that in the prior art.

Specifically, high-pressure hydrogen in the cathode of the hydrogen pumpunit can be supplied to a first space formed between the second endplate and the cathode separator through a first gas flow channel. Thus,the hydrogen gas pressure in the first space is almost as high as thehydrogen gas pressure in the cathode of the hydrogen pump unit. The loadapplied by the hydrogen in the first space to the cathode separatorsuppresses deformation (deflection) of the cathode separator due to thehydrogen gas pressure in the cathode. Therefore, a gap is unlikely to beformed between the cathode separator and the cathode of the hydrogenpump unit, compared with a case in which such a first space is notformed, so that the electrochemical hydrogen pump according to thepresent aspect can easily and appropriately suppress an increase in thecontact resistance between the cathode separator and the cathode of thehydrogen pump unit.

As a result of the inventors' further thorough investigation of thehigh-pressure hydrogen producing apparatus of Japanese Unexamined PatentApplication Publication No. 2006-70322, the inventors found thatpressure applied to the anode separator by the anode power feederdeforms the anode separator so as to curve outward toward theneighboring end plate and accordingly that the end plate also deforms soas to curve outward away from the stack. In the high-pressure hydrogenproducing apparatus of Japanese Unexamined Patent ApplicationPublication No. 2006-70322, the above deformation of the anode separatorforms a gap between the cathode separator and the cathode power feederthat is larger than the gap described in paragraph [0020] of JapaneseUnexamined Patent Application Publication No. 2006-70322. To fill thegap, the distance of the disc spring electrically connecting the cathodepower feeder and the cathode separator to each other increases, andthus, the electrical resistance of the disc spring increases.

In the electrochemical hydrogen pump according to the prior patent bythe applicant, when the gas pressure in the cathode increases, the anodegas diffusion layer 115 deforms in the same manner as in JapaneseUnexamined Patent Application Publication No. 2006-70322. Then, theanode gas flow channel member (not shown) to which pressure is applieddue to the deformation of the anode gas diffusion layer 115 deforms soas to curve outward toward the neighboring end plate (not shown), andaccordingly, the end plate deforms so as to curve outward away from thestack 500. To reliably establish the electrical contact between thecathode gas diffusion layer 114 and the electrolyte membrane 111(cathode catalyst layer 112), the amount of protrusion Ecd of thecathode gas diffusion layer 114 needs to be further increased,considering deformation of members, such as the anode gas flow channelmember and the end plate. As a result, when the gas pressure in thecathode increases, the dimension of the cathode gas diffusion layer 114in a thickness direction increases and the electrical resistance of thecathode gas diffusion layer 114 in the thickness direction increases.Such a problem occurs not only in the above prior patent of theapplicant, but also in a structure in which a cathode gas diffusionlayer is disposed on a flat surface of a cathode separator having noconcave portions.

The inventors found that forming a space between the anode separator andthe anode end plate disposed on the anode separator that communicateswith the cathode easily suppresses the above-described increase in theelectrical resistance between the cathode gas diffusion layer and theelectrolyte membrane (cathode catalyst layer) and have developed oneaspect of the present disclosure as follows.

An electrochemical hydrogen pump according to a second aspect of thepresent disclosure may include a second fixing member for preventingmovement of the anode separator in a direction in which the anodeseparator is stacked and a second gas flow channel through whichhydrogen generated in the cathode is supplied to a second space formedbetween the anode end plate and the anode separator in theelectrochemical hydrogen pump according to the first aspect.

According to such a structure, the electrochemical hydrogen pumpaccording to the present aspect can supply high-pressure hydrogengenerated in the cathode of the hydrogen pump unit to the second spaceformed between the anode end plate and the anode separator through thesecond gas flow channel. Thus, the hydrogen gas pressure in the secondspace is almost as high as the hydrogen gas pressure in the cathode ofthe hydrogen pump unit. The load applied by the hydrogen in the secondspace to the anode separator suppresses deformation of the anodeseparator due to the hydrogen gas pressure in the cathode. Therefore, agap is unlikely to be formed between the cathode and the electrolytemembrane of the hydrogen pump unit, compared with a case in which such asecond space is not formed, so that the electrochemical hydrogen pumpaccording to the present aspect can easily and appropriately suppress anincrease in the contact resistance between the cathode and theelectrolyte membrane of the hydrogen pump unit.

According to an electrochemical hydrogen pump according to a thirdaspect of the present disclosure, the first space and the second spacemay be formed to face each other in the electrochemical hydrogen pumpaccording to the second aspect.

According to such a structure, the load applied by the hydrogen in thefirst space to the cathode separator and the load applied by thehydrogen in the second space to the anode separator uniformly suppressesdeformation, which is due to hydrogen gas pressure in the cathode, inthe surface of each member of the hydrogen pump unit from both ends ofthe hydrogen pump unit. Thus, the electrochemical hydrogen pumpaccording to the present aspect can effectively suppress deformation ofeach member of the hydrogen pump unit, compared with a case in which thefirst space and the second space are not formed to face each other.

The expression “the first space and the second space are formed to faceeach other” means that the first space and the second space are formedsuch that at least a portion of the first space and at least a portionof the second space overlap each other when viewed in the stackingdirection.

According to an electrochemical hydrogen pump in a fourth aspect of thepresent disclosure, the second gas flow channel may include acommunicating channel that connects the first space and the second spaceto each other in the electrochemical hydrogen pump of the second aspector the third aspect.

According to such a structure, the electrochemical hydrogen pump in thepresent aspect can supply high-pressure hydrogen in the cathode of thehydrogen pump unit to the second space through the communicating channelthat connects the first space and the second space to each other.

According to an electrochemical hydrogen pump in a fifth aspect of thepresent disclosure, the first space may be formed parallel to the mainsurface of the cathode of the electrochemical hydrogen pump in any oneof the first aspect to the fourth aspect.

According to such a structure, the load to be applied to the cathodeseparator can be uniformly applied to the surface thereof on the basisof the hydrogen gas pressure in the first space. Thus, in theelectrochemical hydrogen pump in the present aspect, the load applied bythe hydrogen in the first space to the cathode separator effectivelysuppresses deformation of the cathode separator, compared with a case inwhich the first space is not formed parallel to the main surface of thecathode.

According to an electrochemical hydrogen pump in a sixth aspect of thepresent disclosure, the area of an opening of the first space that isparallel to the main surface of the cathode separator may be equal to orlarger than the area of the main surface of the cathode of theelectrochemical hydrogen pump in any one of the first aspect to thefifth aspect.

If the area of an opening of the first space that is parallel to themain surface of the cathode separator is smaller than the area of themain surface of the cathode, deformation due to the hydrogen gaspressure in the cathode may occur in a portion of the cathode separatorthat faces a portion of the cathode that is not overlapped by the firstspace.

In the electrochemical hydrogen pump in the present aspect, the area ofthe opening of the first space is set to be equal to or larger than thearea of the main surface of the cathode, so that the first space canoverlap all of the main surface of the cathode. Therefore, the load isapplied on the basis of the hydrogen gas pressure in the first space toall of a portion of the cathode separator that faces the cathode, andthus, the above risk can be decreased.

According to an electrochemical hydrogen pump in a seventh aspect of thepresent disclosure, the area of an opening of the first space that isparallel to the main surface of the cathode separator may be equal to orsmaller than the area of the main surface of the cathode separator inthe electrochemical hydrogen pump in any one of the first aspect to thesixth aspect.

According to an electrochemical hydrogen pump in an eighth aspect of thepresent disclosure, the second space may be formed parallel to the mainsurface of the anode in the electrochemical hydrogen pump in any one ofthe second aspect to the fourth aspect.

According to such a structure, the load to be applied to the anodeseparator can be uniformly applied to the surface thereof on the basisof the hydrogen gas pressure in the second space. Thus, in theelectrochemical hydrogen pump in the present aspect, the load applied bythe hydrogen in the second space to the anode separator effectivelysuppresses deformation of the anode separator, compared with a case inwhich the second space is not formed parallel to the main surface of theanode.

According to an electrochemical hydrogen pump in a ninth aspect of thepresent disclosure, the area of an opening of the second space that isparallel to the main surface of the anode separator may be equal to orlarger than the area of the main surface of the anode in theelectrochemical hydrogen pump in any one of the second aspect to thefifth aspect.

If the area of an opening of the second space that is parallel to themain surface of the anode separator is smaller than the area of the mainsurface of the anode, deformation due to the hydrogen gas pressure inthe cathode may occur in a portion of the anode separator that faces aportion of the anode that is not overlapped by the second space.

In the electrochemical hydrogen pump in the present aspect, the area ofthe opening of the second space is set to be equal to or larger than thearea of the main surface of the anode, so that the second space canoverlap all of the main surface of the anode. Therefore, the load isapplied on the basis of the hydrogen gas pressure in the second space toall of a portion of the anode separator that faces the anode, and thus,the above risk can be decreased.

According to an electrochemical hydrogen pump in a tenth aspect of thepresent disclosure, the area of an opening of the second space that isparallel to the main surface of the anode separator may be equal to orsmaller than the area of the main surface of the anode separator in theelectrochemical hydrogen pump in any one of the second aspect to thefifth aspect and the ninth aspect.

According to an electrochemical hydrogen pump in an eleventh aspect ofthe present disclosure, the anode may include an anode gas diffusionlayer, the cathode may include a cathode gas diffusion layer, and theelastic modulus of the anode gas diffusion layer may be higher than theelastic modulus of the cathode gas diffusion layer in theelectrochemical hydrogen pump in any one of the first aspect to thetenth aspect.

Hereinafter, with reference to the drawings, embodiments of the presentdisclosure will be described. The embodiments described below eachillustrate an example of the above aspects. Thus, shapes, materials,components, and the positions and connection modes of the components,which will be described below, are examples and do not limit the aboveaspects provided that they are not described in Claims. Among thecomponents described below, components not described in the independentClaim showing the broadest concept of the above aspects are described asoptional components. In the drawings, description of one of componentswith the same symbol may be omitted. In the drawings, the components areschematically drawn to facilitate the understanding, so that shapes anddimensional ratios in the drawings may be different from those of actualcomponents.

First Embodiment Device Structure

FIG. 2A and FIG. 3A are each an image of an exemplary electrochemicalhydrogen pump according to a first embodiment. FIG. 2B is an enlargedview of portion IIB of FIG. 2A. FIG. 3B is an enlarged view of portionIIIB of FIG. 3A.

FIG. 2A illustrates a vertical cross-section of an electrochemicalhydrogen pump 100. The vertical cross-section includes a straight linepassing through the center of the electrochemical hydrogen pump 100 andthe center of a cathode gas discharge manifold 50 in plan view. FIG. 3Aillustrates a vertical cross-section of the electrochemical hydrogenpump 100. The vertical cross-section includes a straight line passingthrough the center of the electrochemical hydrogen pump 100, the centerof an anode gas intake manifold 27, and the center of an anode gasdischarge manifold 30 in plan view.

In the examples illustrated in FIG. 2A and FIG. 3B, the electrochemicalhydrogen pump 100 includes at least one hydrogen pump unit 100A.

In the electrochemical hydrogen pumps 100 illustrated in FIG. 2A andFIG. 3B, three hydrogen pump units 100A are stacked on each other;however, the number of the hydrogen pump units 100A is not limitedthereto. In other words, the number of the hydrogen pump units 100A canbe appropriately determined in accordance with operating conditions,such as the amount of hydrogen pressurized by the electrochemicalhydrogen pump 100.

The hydrogen pump unit 100A includes an electrolyte membrane 11, ananode AN, a cathode CA, a cathode separator 16, an anode separator 17,and an insulator 21.

The anode AN is disposed on one main surface of the electrolyte membrane11. The anode AN is an electrode including an anode catalyst layer 13and an anode gas diffusion layer 15 disposed on the anode catalyst layer13. An annular sealing member 43 is disposed so as to surround theperiphery of the anode catalyst layer 13 in plan view to appropriatelyseal the anode catalyst layer 13.

The cathode CA is disposed on the other main surface of the electrolytemembrane 11. The cathode CA is an electrode including a cathode catalystlayer 12 and a cathode gas diffusion layer 14 disposed on the cathodecatalyst layer 12. An annular sealing member 42 is disposed so as tosurround the periphery of the cathode catalyst layer 12 in plan view toappropriately seal the cathode catalyst layer 12.

Accordingly, the electrolyte membrane 11 is sandwiched between the anodeAN and the cathode CA so as to be in contact with the anode catalystlayer 13 and the cathode catalyst layer 12. A stack of the cathode CA,the electrolyte membrane 11, and the anode AN is referred to as amembrane electrode assembly (hereinafter, MEA).

The electrolyte membrane 11 has proton conductivity. The electrolytemembrane 11 may have any structure provided that the electrolytemembrane 11 has proton conductivity. Examples of the electrolytemembrane 11 include, but are not limited to, fluorine-based polymerelectrolyte membranes and hydrocarbon-based polymer electrolytemembranes. Specifically, Nafion (trade name, manufactured by Du Pont) orAciplex (trade name, manufactured by Asahi Kasei Corp.) may be used asthe electrolyte membrane 11.

The anode catalyst layer 13 is disposed on one main surface of theelectrolyte membrane 11. The catalytic metal contained in the anodecatalyst layer 13 may be, but is not limited to, platinum.

The cathode catalyst layer 12 is disposed on the other main surface ofthe electrolyte membrane 11. The catalytic metal contained in thecathode catalyst layer 12 may be, but is not limited to, platinum.

Examples of a catalyst carrier of the cathode catalyst layer 12 and theanode catalyst layer 13 include, but are not limited to, carbon powders,such as carbon black and graphite, and conductive oxide powders.

In the cathode catalyst layer 12 and the anode catalyst layer 13, highlydispersed catalytic metal particulates are supported on the catalystcarrier. An ionomer component having hydrogen ion conductivity istypically added to the cathode catalyst layer 12 and the anode catalystlayer 13 to increase the electrode reaction area.

The anode gas diffusion layer 15 is formed of a porous material. Theanode gas diffusion layer 15 is conductive and has gas diffusionproperties. The anode gas diffusion layer 15 desirably has highstiffness and can suppress displacement and deformation of componentsdue to a difference in pressure between the cathode CA and the anode ANduring operation of the electrochemical hydrogen pump 100. In otherwords, the elastic modulus of the anode gas diffusion layer 15 is higherthan the elastic modulus of the cathode gas diffusion layer 14.

Examples of the base material of the anode gas diffusion layer 15include sintered bodies of a metal fiber made of a material, such astitanium, a titanium alloy, or stainless steel, sintered bodies of ametal powder made of such a material, expanded metals, metal meshes, andpunching metals.

The cathode gas diffusion layer 14 is formed of a porous material. Thecathode gas diffusion layer 14 is conductive and has gas diffusionproperties. The cathode gas diffusion layer 14 desirably has an elasticmodulus so as to appropriately follow displacement and deformation ofcomponents due to a difference in pressure between the cathode and theanode during operation of the electrochemical hydrogen pump 100. Inother words, the elastic modulus of the cathode gas diffusion layer 14is lower than the elastic modulus of the anode gas diffusion layer 15.

Examples of the base material of the cathode gas diffusion layer 14include sintered bodies of a metal fiber made of a material, such astitanium, a titanium alloy, or stainless steel, and sintered bodies of ametal powder made of such a material. The base material of the cathodegas diffusion layer 14 may be a porous carbon material, such as carbonpaper, carbon cloth, or carbon felt. Furthermore, a porous sheetmaterial obtained by kneading and rolling an elastomer, such as carbonblack or polytetrafluoroethylene (PTFE), may be used.

The anode separator 17 is a member stacked on the anode AN. The cathodeseparator 16 is a member stacked on the cathode CA. The cathodeseparator 16 and the anode separator 17 each have a concave portion inthe center portion thereof. The cathode gas diffusion layer 14 isaccommodated in the concave portion of the cathode separator 16. Theanode gas diffusion layer 15 is accommodated in the concave portion ofthe anode separator 17.

The hydrogen pump unit 100A is formed by sandwiching the MEA between thecathode separator 16 and the anode separator 17, as described above.

In plan view, for example, a serpentine cathode gas flow channel 32including a plurality of U-shaped curve portions and a plurality ofstraight portions is disposed in a main surface of the cathode separator16 that is in contact with the cathode gas diffusion layer 14. Thestraight portions of the cathode gas flow channel 32 extend in adirection perpendicular to the sheet surface of FIG. 2A (directionparallel to the sheet surface of FIG. 3A). The cathode gas flow channel32 is an example, and the cathode gas flow channel is not limitedthereto. For example, the cathode gas flow channel may be formed of aplurality of straight channels.

In plan view, for example, a serpentine anode gas flow channel 33including a plurality of U-shaped curve portions and a plurality ofstraight portions is disposed in a main surface of the anode separator17 that is in contact with the anode gas diffusion layer 15. Thestraight portions of the anode gas flow channel 33 extend in a directionperpendicular to the sheet surface of FIG. 3A (a direction parallel tothe sheet surface of FIG. 2A). The anode gas flow channel 33 is anexample, and the anode gas flow channel is not limited thereto. Forexample, the anode gas flow channel may be formed of a plurality ofstraight channels.

The annular plate-like insulator 21, which is disposed so as to surroundthe periphery of the MEA, is sandwiched between the conductive cathodeseparator 16 and the conductive anode separator 17. Thus, a shortcircuit between the cathode separator 16 and the anode separator 17 isprevented.

As shown in FIG. 2A and FIG. 3A, the electrochemical hydrogen pump 100includes a first fixing member for preventing movement of the cathodeseparator 16 in a direction in which the cathode separator 16 isstacked, a second fixing member for preventing movement of the anodeseparator 17 in a direction in which the anode separator 17 is stacked,an anode end plate 24A, and a cathode end plate 24C.

The anode end plate 24A is a member disposed on the anode separator 17positioned at one end in a direction in which the cathode separator 16is stacked. The expression “on the anode separator 17” means on a mainsurface of a pair of the main surfaces of the anode separator 17 thatfaces away from the anode AN. The cathode end plate 24C is a memberdisposed on the cathode separator 16 positioned at the other end in adirection in which the cathode separator 16 is stacked. The expression“on the cathode separator 16” means on a main surface of a pair of themain surfaces of the cathode separator 16 that faces away from thecathode CA.

The first fixing member may have any structure provided that the firstfixing member fixes the cathode separator 16 in a direction in which thecathode separator 16 is stacked. For example, as shown in FIG. 2A andFIG. 3A, the first fixing member may be a fastener 25 used for applyingfastening pressure to the hydrogen pump unit 100A. Examples of thefastener 25 include bolts and nuts with a disc spring.

The second fixing member may have any structure provided that the secondfixing member fixes the anode separator 17 in a direction in which theanode separator 17 is stacked. For example, as shown in FIG. 2A and FIG.3A, the second fixing member may be the fastener 25.

The bolt of the fastener 25 may be configured to pass through only theanode end plate 24A and the cathode end plate 24C; however, in theelectrochemical hydrogen pump 100 according to the present embodiment,the bolt passes through each member of the three stacked hydrogen pumpunits 100A, a cathode power feeder plate 22C, a cathode insulating plate23C, an anode power feeder plate 22A, an anode insulating plate 23A, theanode end plate 24A, and the cathode end plate 24C. The fastener 25applies a desired fastening pressure to the hydrogen pump units 100Asandwiched between the cathode end plate 24C and the anode end plate 24Ain a state in which the cathode end plate 24C presses the end surface ofthe cathode separator 16 positioned at the other end in the stackingdirection, with the cathode power feeder plate 22C and the cathodeinsulating plate 23C disposed between the cathode end plate 24C and thecathode separator 16, and in which the anode end plate 24A presses theend surface of the anode separator 17 positioned at one end in thestacking direction, with the anode power feeder plate 22A and the anodeinsulating plate 23A disposed between the anode end plate 24A and theanode separator 17.

Accordingly, the fastening pressure of the fastener 25 appropriatelyholds the multi-stacked (three in this instance) hydrogen pump units100A in a stacked state in the stacking direction, and the bolt of thefastener 25 passes through each member of the electrochemical hydrogenpump 100. Thus, movement of such a member in an in-plane direction isappropriately suppressed.

Here, a sealing material made of resin (not shown and not described indetail) may be disposed on the side surface of each member of theelectrochemical hydrogen pump, instead of using the fastener 25, to fixthe electrochemical hydrogen pump.

As shown in FIG. 2A and FIG. 3A, the electrochemical hydrogen pump 100includes a first gas flow channel through which hydrogen in the cathodeCA is supplied to a first space 60 formed between the cathode end plate24C and the cathode separator 16.

The first space 60 may be any space formed between the cathode end plate24C and the cathode separator 16. The first gas flow channel may haveany structure provided that the hydrogen in the cathode CA is suppliedto the first space 60 through the first gas flow channel.

For example, in the electrochemical hydrogen pump 100 according to thepresent embodiment, as shown in FIG. 2A, the first gas flow channelincludes the cylindrical cathode gas discharge manifold 50 and a cathodegas supplying channel 51 connecting the cathode gas discharge manifold50 and the first space 60 to each other.

Here, the first space 60 includes a concave portion disposed in thecenter portion of the cathode end plate 24C and an opening formed in thecenter portion of the cathode insulating plate 23C.

The cathode gas discharge manifold 50 includes a through-hole formed ineach member of the three stacked hydrogen pump units 100A and anon-through hole formed in the anode end plate 24A and the cathode endplate 24C, and the through-holes and the non-through holes are connectedto each other.

The cathode gas supplying channel 51 includes a groove formed in themain surface of the cathode end plate 24C that connects the concaveportion (the first space 60) of the cathode end plate 24C and the otherend of the cathode gas discharge manifold 50 to each other.

As shown in FIG. 2A, a cathode gas discharge channel 26 is disposed soas to pass through the cathode end plate 24C. The cathode gas dischargechannel 26 may include a pipe through which hydrogen (H₂) dischargedfrom the cathode CA flows. The cathode gas discharge channel 26communicates with the first space 60. Accordingly, the cathode gasdischarge channel 26 communicates with the cathode gas dischargemanifold 50 through the first space 60 and the cathode gas supplyingchannel 51.

The cathode gas discharge manifold 50 communicates with one end of thecathode gas flow channel 32 through a cathode gas passing channel 34 inthe hydrogen pump unit 100A. Accordingly, hydrogen that has passedthrough the cathode gas flow channel 32 and the cathode gas passingchannel 34 of each hydrogen pump unit 100A is collected in the cathodegas discharge manifold 50. Then, the collected hydrogen passes throughthe cathode gas supplying channel 51 and the first space 60 in thisorder and flows to the cathode gas discharge channel 26. In such amanner, high-pressure hydrogen flows through the first space 60.

In plan view, an annular sealing member 40, such as an O-ring, isdisposed between the cathode separator 16 and the anode separator 17,the cathode separator 16 and the cathode power feeder plate 22C, and theanode separator 17 and the anode power feeder plate 22A, so as tosurround the cathode gas discharge manifold 50 to appropriately seal thecathode gas discharge manifold 50.

As shown in FIG. 3A, an anode gas intake channel 29 is disposed on theanode end plate 24A. The anode gas intake channel 29 may include a pipethrough which hydrogen (H₂) to be supplied to the anode AN flows. Theanode gas intake channel 29 communicates with the cylindrical anode gasintake manifold 27. The anode gas intake manifold 27 includes athrough-hole formed in each member of the three stacked hydrogen pumpunits 100A and the anode end plate 24A, and the through-holes areconnected to each other.

The anode gas intake manifold 27 communicates with one end of the anodegas flow channel 33 through a first anode gas passing channel 35 in thehydrogen pump unit 100A. Accordingly, hydrogen supplied from the anodegas intake channel 29 to the anode gas intake manifold 27 is distributedto the hydrogen pump units 100A through the respective first anode gaspassing channels 35. While the distributed hydrogen passes through theanode gas flow channels 33, hydrogen is supplied from the anode gasdiffusion layer 15 to the anode catalyst layer 13.

As shown in FIG. 3A, an anode gas discharge channel 31 is disposed onthe anode end plate 24A. The anode gas discharge channel 31 may includea pipe through which hydrogen (H₂) discharged from the anode AN flows.The anode gas discharge channel 31 communicates with the cylindricalanode gas discharge manifold 30. The anode gas discharge manifold 30includes a through-hole formed in each member of the three stackedhydrogen pump units 100A and the anode end plate 24A, and thethrough-holes are connected to each other.

The anode gas discharge manifold 30 communicates with the other end ofthe anode gas flow channel 33 through a second anode gas passing channel36 in the hydrogen pump unit 100A. Accordingly, hydrogen that has passedthrough the anode gas flow channel 33 of each hydrogen pump unit 100A issupplied to and collected in the anode gas discharge manifold 30 throughthe second anode gas passing channel 36. Then, the collected hydrogenflows to the anode gas discharge channel 31.

In plan view, the annular sealing member 40, such as an O-ring, isdisposed between the cathode separator 16 and the anode separator 17,between the cathode separator 16 and the cathode power feeder plate 22C,and between the anode separator 17 and the anode power feeder plate 22A,so as to surround the anode gas intake manifold 27 and the anode gasdischarge manifold 30 to appropriately seal the anode gas intakemanifold 27 and the anode gas discharge manifold 30.

As shown in FIG. 2A and FIG. 3A, the electrochemical hydrogen pump 100includes a voltage application unit 102.

The voltage application unit 102 is a device that applies a voltagebetween the anode AN and the cathode CA. Specifically, the voltageapplication unit 102 applies a high potential to the conductive anode ANand a low potential to the conductive cathode CA. The voltageapplication unit 102 may have any structure provided that the voltageapplication unit 102 applies a voltage between the anode AN and thecathode CA. For example, the voltage application unit 102 may be adevice that adjusts the voltage to be applied between the anode AN andthe cathode CA. In such a case, the voltage application unit 102includes a DC/DC converter when connected to a direct-current powersource, such as a battery, a solar cell, or a fuel cell, or an AC/DCconverter when connected to an alternating-current power source, such asa commercial power source.

In examples shown in FIG. 2A and FIG. 3A, the low potential terminal ofthe voltage application unit 102 is connected to the cathode powerfeeder plate 22C, and the high potential terminal of the voltageapplication unit 102 is connected to the anode power feeder plate 22A.The cathode power feeder plate 22C is in an electrical contact with thecathode separator 16 positioned at the other end in the stackingdirection. The anode power feeder plate 22A is in an electrical contactwith the anode separator 17 positioned at one end in the stackingdirection.

A hydrogen supply system (not shown) including the electrochemicalhydrogen pump 100 can be established. In such a case, a device neededfor hydrogen supply operation of the hydrogen supply system isappropriately disposed in the system.

For example, the hydrogen supply system may include a dew pointadjusting unit (e.g., humidifier) that adjusts the dew point of a gasmixture containing hydrogen (H₂) having high humidity discharged fromthe anode AN through the anode gas discharge channel 31 and hydrogen(H₂) having low humidity supplied from an external hydrogen supplierthrough the anode gas intake channel 29. In such a case, the hydrogensupplied from an external hydrogen supplier may be generated by, forexample, a water electrolysis device.

For example, the hydrogen supply system may include a temperaturemeasuring unit that measures the temperature of the electrochemicalhydrogen pump 100, a hydrogen storage unit that temporarily storeshydrogen discharged from the cathode CA of the electrochemical hydrogenpump 100, and a pressure measuring unit that measures hydrogen gaspressure in the hydrogen storage unit.

Note that the above structure of the electrochemical hydrogen pump 100and various units and devices (not shown) in the hydrogen supply systemare examples, and the present disclosure is not limited to the examples.

For example, a dead-end structure in which the anode gas dischargemanifold 30 and the anode gas discharge channel 31 are not disposed andin which all hydrogen to be supplied to the anode AN through the anodegas intake manifold 27 is pressurized in the cathode CA may be used. Asdescribed above, hydrogen (H₂) flows, for example, through the anode gasflow channel 33 and the cathode gas flow channel 32; however, “hydrogen”is not necessarily 100% hydrogen. A gas containing hydrogen may flow.

Operation

Hereinafter, an exemplary hydrogen pressurizing operation of theelectrochemical hydrogen pump 100 will be described with reference tothe drawings.

The following operation may be performed such that the arithmeticcircuit of a controlling unit (not shown) reads out a controllingprogram from the memory circuit of the controlling unit. The followingoperation does not need to be performed by a controlling unit. Thefollowing operation may be partially performed by an operator.

First, low-pressure hydrogen is supplied to the anode AN of theelectrochemical hydrogen pump 100, and a voltage is applied by thevoltage application unit 102 to the electrochemical hydrogen pump 100.

Then, in the anode catalyst layer 13 of the anode AN, a hydrogenmolecule is separated by the oxidation reaction into hydrogen ions(protons) and electrons (Formula (1)). The protons transfer to thecathode catalyst layer 12 through the electrolyte membrane 11. Theelectrons transfer to the cathode catalyst layer 12 through the voltageapplication unit 102.

Then, in the cathode catalyst layer 12, a hydrogen molecule isregenerated by the reduction reaction (Formula (2)). It is known thatwhen the protons transfer through the electrolyte membrane 11, a certainamount of water (i.e., electro-osmotic water) transfers with the protonsfrom the anode AN to the cathode CA.

At this time, hydrogen generated in the cathode CA can be pressurized byincreasing pressure loss in a hydrogen discharge channel (e.g., cathodegas discharge channel 26 in FIG. 2A) by using a flow-rate adjusting unit(not shown) (e.g., a back-pressure valve or a regulating valve disposedin a pipe). Then, high-pressure hydrogen generated in the cathode CA issupplied to the first space 60 formed between the cathode end plate 24Cand the cathode separator 16 through the cathode gas discharge manifold50 and the cathode gas supplying channel 51.

anode: H₂(low pressure)→2H⁺2e ⁻  (1)

cathode: 2H⁺2e ⁻→H₂(high pressure)  (2)

In such away, in the electrochemical hydrogen pump 100, applying avoltage by using the voltage application unit 102 leads topressurization of hydrogen to be supplied to the anode AN in the cathodeCA. Accordingly, hydrogen pressurizing operation of the electrochemicalhydrogen pump 100 is performed, and the hydrogen pressurized in thecathode CA is temporarily stored in, for example, a hydrogen storageunit (not shown). The hydrogen stored in the hydrogen storage unit istimely supplied to a hydrogen demanding object. Examples of the hydrogendemanding object include fuel cells that generate power by usinghydrogen.

Here, in the above hydrogen pressurizing operation of theelectrochemical hydrogen pump 100, gas pressure is increased in thecathode CA, and thus, the electrolyte membrane 11, the anode catalystlayer 13, and the anode gas diffusion layer 15 are pressed. Then, thepressing force compresses the electrolyte membrane 11, the anodecatalyst layer 13, and the anode gas diffusion layer 15.

At this time, if adhesion between the cathode catalyst layer 12 and thecathode gas diffusion layer 14 is low, a gap is likely to be formedtherebetween. If a gap is formed between the cathode catalyst layer 12and the cathode gas diffusion layer 14, the contact resistancetherebetween increases. Then, an increase in a voltage applied by thevoltage application unit 102 may cause degradation of the operationefficiency of the electrochemical hydrogen pump 100.

Before the hydrogen pump unit 100A is fastened by the fastener 25, thecathode gas diffusion layer 14 is configured to protrude by apredetermined amount of protrusion from the concave portion of thecathode separator 16 in the thickness direction. When the hydrogen pumpunit 100A is fastened, the cathode gas diffusion layer 14 is compressedby the amount of protrusion by the fastening force of the fastener 25.

If the electrolyte membrane 11, the anode catalyst layer 13, and theanode gas diffusion layer 15 are each compressed and deform duringoperation of the electrochemical hydrogen pump 100, the cathode gasdiffusion layer 14 elastically deforms in a direction in which thethickness after the compression by the fastener 25 returns to theoriginal thickness before the compression, so that the contact betweenthe cathode catalyst layer 12 and the cathode gas diffusion layer 14 isappropriately maintained in the electrochemical hydrogen pump 100according to the present embodiment.

The electrochemical hydrogen pump 100 according to the presentembodiment can easily and appropriately suppress an increase in thecontact resistance between the cathode separator 16 and the cathode CAof the hydrogen pump unit 100A, compared with that in the prior art.

Specifically, high-pressure hydrogen in the cathode CA of the hydrogenpump unit 100A can be supplied to the first space 60 formed between thecathode end plate 24C and the cathode separator 16 through the cathodegas discharge manifold 50 and the cathode gas supplying channel 51.Thus, hydrogen gas pressure in the first space 60 is almost as high asthe hydrogen gas pressure in the cathode CA of the hydrogen pump unit100A. The load applied by the hydrogen in the first space 60 to thecathode separator 16 suppresses deformation of the cathode separator 16due to hydrogen gas pressure in the cathode CA. Thus, a gap is unlikelyto be formed between the cathode separator 16 and the cathode CA of thehydrogen pump unit 100A, compared with a case in which the first space60 is not formed, so that the electrochemical hydrogen pump 100according to the present embodiment can easily and appropriatelysuppress an increase in the contact resistance between the cathodeseparator 16 and the cathode CA of the hydrogen pump unit 100A.

First Example

The electrochemical hydrogen pump 100 in the present example is the sameas the electrochemical hydrogen pump 100 according to the firstembodiment, except that the first space 60 is formed parallel to themain surface of the cathode CA.

According to such a structure, the load to be applied to the cathodeseparator 16 can be uniformly applied to the surface thereof on thebasis of the hydrogen gas pressure in the first space 60. Thus, in theelectrochemical hydrogen pump 100 in the present example, a load appliedby the hydrogen in the first space 60 to the cathode separator 16effectively suppresses deformation (deflection) of the cathode separator16, compared with a case in which the first space 60 is not formedparallel to the main surface of the cathode CA.

The electrochemical hydrogen pump 100 in the present example may be thesame as the electrochemical hydrogen pump 100 according to the firstembodiment, except for the above feature.

Second Example

The electrochemical hydrogen pump 100 in the present example is the sameas the electrochemical hydrogen pump 100 according to the firstembodiment, except that the area of an opening of the first space 60that is parallel to the main surface of the cathode separator 16 isequal to or larger than the area of the main surface of the cathode CA.Note that the area of such an opening of the first space 60 is equal toor smaller than the area of the main surface of the cathode separator16.

If the area of an opening of the first space 60 that is parallel to themain surface of the cathode separator 16 is smaller than the area of themain surface of the cathode CA (i.e., area of the opening of the firstspace 60<area of the main surface of the cathode CA), deformation due tothe hydrogen gas pressure in the cathode CA may occur in a portion ofthe cathode separator 16 that faces a portion of the cathode CA that isnot overlapped by the first space 60.

In the electrochemical hydrogen pump 100 in the present example, thearea of the opening of the first space 60 is set to be equal to orlarger than the area of the main surface of the cathode CA (i.e., areaof the opening of the first space 60 area of the main surface of thecathode CA), so that the first space 60 can overlap all the area of themain surface of the cathode CA. Therefore, the load is applied on thebasis of the hydrogen gas pressure in the first space 60 to all of aportion of the cathode separator 16 that faces the cathode CA, and thus,the above risk can be decreased.

The electrochemical hydrogen pump 100 in the present example may be thesame as the electrochemical hydrogen pump 100 according to the firstembodiment or the electrochemical hydrogen pump 100 in the first exampleof the first embodiment, except for the above feature.

Modified Example

FIG. 4 is an exemplary electrochemical hydrogen pump in a modifiedexample of the first embodiment.

FIG. 4 illustrates a vertical cross-section of the electrochemicalhydrogen pump 100. The vertical cross-section includes a straight linepassing through the center of the electrochemical hydrogen pump 100 andthe center of the cathode gas discharge manifold 50 in plan view.

The electrochemical hydrogen pump 100 in the present modified example isthe same as the electrochemical hydrogen pump 100 according to the firstembodiment, except for the position of a cathode gas discharge channel26A, which will be described below.

In the electrochemical hydrogen pump 100 in the present modifiedexample, the cathode gas discharge channel 26A is disposed so as toextend from the cathode gas discharge manifold 50 and is different fromthe cathode gas discharge channel 26 in FIG. 2A, which is disposed so asto extend from the first space 60.

In this case, the cathode gas discharge manifold 50 includes athrough-hole formed in each member of the three stacked hydrogen pumpunits 100A and the cathode end plate 24C and a non-through hole formedin the anode end plate 24A, and the through-holes and the non-throughhole are connected to each other.

Accordingly, the electrochemical hydrogen pump 100 in the presentmodified example can supply high-pressure hydrogen in the cathode CA ofthe hydrogen pump unit 100A to the first space 60 formed between thecathode end plate 24C and the cathode separator 16 through the cathodegas discharge manifold 50 and the cathode gas supplying channel 51. Inother words, high-pressure hydrogen is retained in the first space 60.

The electrochemical hydrogen pump 100 in the present modified exampleexhibits the same advantages as the electrochemical hydrogen pump 100according to the first embodiment, and thus, the detailed description isomitted.

The electrochemical hydrogen pump 100 in the present modified examplemay be the same as the electrochemical hydrogen pump 100 according tothe first embodiment, or the electrochemical hydrogen pump 100 in thefirst example or the second example of the first embodiment, except forthe above feature.

Second Embodiment

FIG. 5 illustrates an exemplary electrochemical hydrogen pump accordingto a second embodiment.

FIG. 5 illustrates a vertical cross-section of the electrochemicalhydrogen pump 100. The vertical cross-section includes a straight linepassing through the center of the electrochemical hydrogen pump 100 andthe center of the cathode gas discharge manifold 50 in plan view.

The electrochemical hydrogen pump 100 according to the presentembodiment is the same as the electrochemical hydrogen pump 100according to the first embodiment, except that a second space 61 and asecond gas flow channel, which will be described below, are included.

As shown in FIG. 5, the electrochemical hydrogen pump 100 includes asecond gas flow channel through which hydrogen generated in the cathodeCA (see FIG. 2B) is supplied to the second space 61 formed between theanode end plate 24A and the anode separator 17.

The second space 61 may be any space formed between the anode end plate24A and the anode separator 17. The second gas flow channel may have anystructure provided that the hydrogen in the cathode CA is supplied tothe second space 61 through the second gas flow channel.

For example, in the electrochemical hydrogen pump 100 according to thepresent embodiment, as shown in FIG. 5, the second gas flow channelincludes the cylindrical cathode gas discharge manifold 50 and a cathodegas supplying channel 52 connecting the cathode gas discharge manifold50 and the second space 61 to each other. Another exemplary second gasflow channel will be described in a modified example.

Here, the second space 61 includes a concave portion disposed in thecenter portion of the anode end plate 24A and an opening formed in thecenter portion of the anode insulating plate 23A.

The cathode gas discharge manifold 50 includes a through-hole formed ineach member of the three stacked hydrogen pump units 100A and anon-through hole formed in the anode end plate 24A and the cathode endplate 24C, and the through-holes and the non-through holes are connectedto each other, in the same manner as in the first embodiment.

The cathode gas supplying channel 52 includes a groove formed in themain surface of the anode end plate 24A that connects the concaveportion (the second space 61) of the anode end plate 24A and one end ofthe cathode gas discharge manifold 50 to each other.

As described above, the electrochemical hydrogen pump 100 according tothe present embodiment can supply high-pressure hydrogen in the cathodeCA of the hydrogen pump unit 100A to the second space 61 formed betweenthe anode end plate 24A and the anode separator 17 through the cathodegas discharge manifold 50 and the cathode gas supplying channel 52.Thus, hydrogen gas pressure in the second space 61 is almost as high asthe hydrogen gas pressure in the cathode CA of the hydrogen pump unit100A. The load applied by the hydrogen in the second space 61 to theanode separator 17 suppresses deformation of the anode separator 17 dueto hydrogen gas pressure in the cathode CA. Thus, a gap is unlikely tobe formed between the cathode gas diffusion layer 14 of the cathode CAand the electrolyte membrane 11 (i.e., in the cathode catalyst layer 12)of the hydrogen pump unit 100A, compared with a case in which the secondspace 61 is not formed, and therefore, the electrochemical hydrogen pump100 according to the present embodiment can easily and appropriatelysuppress an increase in the contact resistance therebetween.

When the electrolyte membrane 11 is, for example, a polymer electrolytemembrane, the polymer electrolyte membrane exhibits a desired protonconductivity in a wet state. Thus, to maintain a desired efficiency ofthe hydrogen pressurizing operation of the electrochemical hydrogen pump100, the electrolyte membrane 11 needs to be maintained in a wet state.If the anode gas flow channel 33 (see FIG. 2B) of the anode separator17, for example, is clogged with water, hydrogen supply in the hydrogenpump unit 100A is prevented. In other words, stabilizing the flow ofhydrogen passing through the anode gas flow channel 33 is an importantfactor for a high-efficient hydrogen pressurizing operation of theelectrochemical hydrogen pump 100. In the electrochemical hydrogen pump100 according to the present embodiment, deformation of the anodeseparator 17 is suppressed regardless of the pressure of hydrogen gas inthe cathode CA of the hydrogen pump unit 100A, compared with a case inwhich the second space 61 is not formed, and thus, the flow of hydrogenpassing through the anode gas flow channel 33, which passes through theanode separator 17, can be appropriately stabilized.

The electrochemical hydrogen pump 100 according to the presentembodiment may be the same as the electrochemical hydrogen pump 100according to the first embodiment or the electrochemical hydrogen pump100 in the first, second, or modified examples of the first embodiment,except for the above feature.

First Example

The electrochemical hydrogen pump 100 in the present example is the sameas the electrochemical hydrogen pump 100 according to the secondembodiment, except that the first space 60 and the second space 61 areformed to face each other.

According to such a structure, the load applied by the hydrogen in thefirst space 60 to the cathode separator 16 and the load applied by thehydrogen in the second space 61 to the anode separator 17 uniformlysuppress deformation, which is due to hydrogen gas pressure in thecathode CA, in the surface of each member of the hydrogen pump unit 100Afrom both ends of the hydrogen pump unit 100A.

Thus, the electrochemical hydrogen pump 100 in the present example caneffectively suppress deformation of each member of the hydrogen pumpunit 100A, compared with a case in which the first space 60 and thesecond space 61 are not formed to face each other.

The electrochemical hydrogen pump 100 in the present example may be thesame as the electrochemical hydrogen pump 100 according to the secondembodiment, except for the above feature.

Second Example

The electrochemical hydrogen pump 100 in the present example is the sameas the electrochemical hydrogen pump 100 according to the secondembodiment, except that the second space 61 is formed parallel to themain surface of the anode AN (see FIG. 2B).

According to such a structure, the load to be applied to the anodeseparator 17 can be uniformly applied to the surface thereof on thebasis of the hydrogen gas pressure in the second space 61. Thus, in theelectrochemical hydrogen pump 100 in the present example, the loadapplied by the hydrogen in the second space 61 to the anode separator 17effectively suppresses deformation (deflection) of the anode separator17, compared with a case in which the second space 61 is not formedparallel to the main surface of the anode AN.

The electrochemical hydrogen pump 100 in the present example may be thesame as the electrochemical hydrogen pump 100 according to the secondembodiment or the electrochemical hydrogen pump 100 in the first exampleof the second embodiment, except for the above feature.

Third Example

The electrochemical hydrogen pump 100 in the present example is the sameas the electrochemical hydrogen pump 100 according to the secondembodiment, except that the area of an opening of the second space 61that is parallel to the main surface of the anode separator 17 is equalto or larger than the area of the main surface of the anode AN (see FIG.2B). Note that the area of such an opening of the second space 61 isequal to or smaller than the area of the main surface of the anodeseparator 17.

If the area of an opening of the second space 61 that is parallel to themain surface of the anode separator 17 is smaller than the area of themain surface of the anode AN (i.e., area of the opening of the secondspace 61<area of the main surface of the anode AN), deformation due tothe hydrogen gas pressure in the cathode CA may occur in a portion ofthe anode separator 17 that faces a portion of the anode AN that is notoverlapped by the second space 61.

In the electrochemical hydrogen pump 100 in the present example, thearea of the opening of the second space 61 is set to be equal to orlarger than the area of the main surface of the anode AN (i.e., area ofthe opening of the second space 61 area of the main surface of the anodeAN), so that the second space 61 can overlap all the area of the mainsurface of the anode AN. Therefore, the load is applied on the basis ofthe hydrogen gas pressure in the second space 61 to all of a portion ofthe anode separator 17 that faces the anode AN, and thus, the above riskcan be decreased.

The electrochemical hydrogen pump 100 in the present example may be thesame as the electrochemical hydrogen pump 100 according to the secondembodiment or the electrochemical hydrogen pump 100 in the first exampleor the second example of the second embodiment, except for the abovefeature.

Modified Example

FIG. 6 is an exemplary electrochemical hydrogen pump in a modifiedexample of the second embodiment.

FIG. 6 illustrates a vertical cross-section of the electrochemicalhydrogen pump 100. The vertical cross-section includes a straight linepassing through the center of the electrochemical hydrogen pump 100 andthe center of the cathode gas discharge manifold 50 in plan view.

The electrochemical hydrogen pump 100 according to the present modifiedexample is the same as the electrochemical hydrogen pump 100 accordingto the second embodiment, except for the structure of a second gas flowchannel, which will be described below.

In the electrochemical hydrogen pump 100 according to the presentmodified example, the second gas flow channel includes a communicatingchannel that connects the first space 60 and the second space 61 to eachother. In this case, the cathode gas supplying channel 52 (see FIG. 5)that connects the cathode gas discharge manifold 50 and the second space61 to each other does not need to be formed.

Specifically, for example, as shown in FIG. 6, a communicating channelmember 70 branching from a cathode gas discharge pipe 26B included inthe cathode gas discharge channel 26 passes through the anode end plate24A and extends to the second space 61. In other words, in the exampleshown in FIG. 6, the communicating channel member 70 is a memberconnecting the first space 60 and the second space 61 to each other;however, the structure of the communicating channel member is notlimited thereto. For example, the communicating channel member may passthrough the cathode end plate 24C and the anode end plate 24A withoutbranching from the cathode gas discharge pipe 26B.

Accordingly, the electrochemical hydrogen pump 100 in the presentmodified example supplies high-pressure hydrogen in the cathode CA ofthe hydrogen pump unit 100A to the second space 61 formed between theanode end plate 24A and the anode separator 17 through the communicatingchannel member 70.

The electrochemical hydrogen pump 100 in the present modified exampleexhibits the same advantages as the electrochemical hydrogen pump 100according to the second embodiment, and thus, the detailed descriptionis omitted.

The electrochemical hydrogen pump 100 in the present modified examplemay be the same as the electrochemical hydrogen pump 100 according tothe second embodiment or the electrochemical hydrogen pump 100 in anyone of the first to third examples of the second embodiment, except forthe above feature.

The first embodiment, the first and second examples of the firstembodiment, the modified example of the first embodiment, the secondembodiment, the first to third examples of the second embodiment, andthe modified example of the second embodiment may be combined with eachother provided that they are compatible with each other.

From the above description, those skilled in the art will appreciatenumerous modifications and other embodiments of the present disclosure.Accordingly, the above description is understood to be illustrative onlyand is provided to teach those skilled in the art the best mode toperform the present disclosure. The structure and/or function may besubstantially changed within the spirit of the present disclosure.

An aspect of the present disclosure can be applied to an electrochemicalhydrogen pump that can easily and appropriately suppress an increase,compared with that in the prior art, in the contact resistance between acathode separator and a cathode of the hydrogen pump unit.

What is claimed is:
 1. An electrochemical hydrogen pump comprising: atleast one hydrogen pump unit including an electrolyte membrane, an anodein contact with one main surface of the electrolyte membrane, a cathodein contact with another main surface of the electrolyte membrane, ananode separator stacked on the anode, and a cathode separator stacked onthe cathode, the at least one hydrogen pump unit transferring, to thecathode, hydrogen contained in a hydrogen-containing gas supplied to theanode and pressurizing the hydrogen; a first fixing member forpreventing movement of the cathode separator in a direction in which thecathode separator is stacked; a first end plate disposed on the anodeseparator positioned at one end in the stacking direction; a second endplate disposed on the cathode separator positioned at another end in thestacking direction; and a first gas flow channel through which hydrogenin the cathode is supplied to a first space formed between the secondend plate and the cathode separator.
 2. The electrochemical hydrogenpump according to claim 1, comprising: a second fixing member forpreventing movement of the anode separator in a direction in which theanode separator is stacked; and a second gas flow channel through whichhydrogen in the cathode is supplied to a second space formed between theanode end plate and the anode separator.
 3. The electrochemical hydrogenpump according to claim 2, wherein the first space and the second spaceare formed to face each other.
 4. The electrochemical hydrogen pumpaccording to claim 2, wherein the second gas flow channel includes acommunicating channel that connects the first space and the second spaceto each other.
 5. The electrochemical hydrogen pump according to claim1, wherein the first space is formed parallel to a main surface of thecathode.
 6. The electrochemical hydrogen pump according to claim 1,wherein an area of an opening of the first space that is parallel to amain surface of the cathode separator is equal to or larger than an areaof a main surface of the cathode.
 7. The electrochemical hydrogen pumpaccording to claim 1, wherein an area of an opening of the first spacethat is parallel to a main surface of the cathode separator is equal toor smaller than an area of the main surface of the cathode separator. 8.The electrochemical hydrogen pump according to claim 2, wherein thesecond space is formed parallel to a main surface of the anode.
 9. Theelectrochemical hydrogen pump according to claim 2, wherein an area ofan opening of the second space that is parallel to a main surface of theanode separator is equal to or larger than an area of a main surface ofthe anode.
 10. The electrochemical hydrogen pump according to claim 2,wherein an area of an opening of the second space that is parallel to amain surface of the anode separator is equal to or smaller than an areaof the main surface of the anode separator.
 11. The electrochemicalhydrogen pump according to claim 1, wherein the anode includes an anodegas diffusion layer, the cathode includes a cathode gas diffusion layer,and an elastic modulus of the anode gas diffusion layer is higher thanan elastic modulus of the cathode gas diffusion layer.